If you haven't installed the Google Play services SDK yet, go get it now by following the guide
to Adding SDK Packages.

To test your app when using the Google Play services SDK, you must use either:

A compatible Android
device that runs Android 2.3 or higher and includes Google Play Store.

The Android emulator with an AVD
that runs the Google APIs platform based on Android 4.2.2 or higher.

Add Google Play Services to Your Project

To make the Google Play services APIs available to your app:

Open the build.gradle file inside your application module directory.

Note: Android Studio projects contain a top-level
build.gradle file and a build.gradle file for each module.
Be sure to edit the file for your application module. See
Building Your Project with
Gradle for more information about Gradle.

Add a new build rule under dependencies for the latest version of
play-services. For example:

Be sure you update this version number each time Google Play services is updated.

Note: If the number of method references in your app exceeds the
65K limit, your app may fail to compile. You
may be able to mitigate this problem when compiling your app by specifying only the specific Google
Play services APIs your app uses, instead of all of them. For information on how to do this,
see Selectively compiling APIs into your executable.

Save the changes and click Sync Project with Gradle Files
in the toolbar.

Open your app's manifest file and add the following tag as a child of the <application>
element:

Selectively compiling APIs into your executable

In versions of Google Play services prior to 6.5, you had to compile the entire package of APIs
into your app. In some cases, doing so made it more difficult to keep the number of methods
in your app (including framework APIs, library methods, and your own code) under the 65,536 limit.

From version 6.5, you can instead selectively compile Google Play service APIs into your app. For
example, to include only the Google Fit and Android Wear APIs, replace the following line in your
build.gradle file:

Table 1 shows a list of the separate APIs that you can include when compiling your app, and
how to describe them in your build.gradle file. Some APIs do not have a separate
library; include them by including the base library. (This lib is automatically included when
you include an API that does have a separate library.)

Table 1. Individual APIs and corresponding build.gradle descriptions.

Google Play services API

Description in build.gradle

Google+

com.google.android.gms:play-services-plus:7.0.0

Google Account Login

com.google.android.gms:play-services-identity:7.0.0

Google Actions, Base Client Library

com.google.android.gms:play-services-base:7.0.0

Google App Indexing

com.google.android.gms:play-services-appindexing:7.0.0

Google Analytics

com.google.android.gms:play-services-analytics:7.0.0

Google Cast

com.google.android.gms:play-services-cast:7.0.0

Google Cloud Messaging

com.google.android.gms:play-services-gcm:7.0.0

Google Drive

com.google.android.gms:play-services-drive:7.0.0

Google Fit

com.google.android.gms:play-services-fitness:7.0.0

Google Location, Activity Recognition, and Places

com.google.android.gms:play-services-location:7.0.0

Google Maps

com.google.android.gms:play-services-maps:7.0.0

Google Mobile Ads

com.google.android.gms:play-services-ads:7.0.0

Google Nearby

com.google.android.gms:play-services-nearby:7.0.0

Google Panorama Viewer

com.google.android.gms:play-services-panorama:7.0.0

Google Play Game services

com.google.android.gms:play-services-games:7.0.0

SafetyNet

com.google.android.gms:play-services-safetynet:7.0.0

Google Wallet

com.google.android.gms:play-services-wallet:7.0.0

Android Wear

com.google.android.gms:play-services-wearable:7.0.0

To make the Google Play services APIs available to your app:

Copy the library project at
<android-sdk>/extras/google/google_play_services/libproject/google-play-services_lib/
to the location where you maintain your Android app projects.

Note: When using Android Studio, you must add Proguard
to your build.gradle file's build types. For more information, see the
Gradle Plugin User Guide.

Ensure Devices Have the Google Play services APK

As described in the Google Play services
introduction, Google Play delivers service updates for users on
Android 2.3 and higher through the Google Play Store app. However, updates might not reach
all users immediately, so your app should verify the version available before attempting to
perform API transactions.

Important:
Because it is hard to anticipate the state of each device, you must always check for a
compatible Google Play services APK before you access Google Play services
features.

Because each app uses Google Play services differently, it's up to you decide the appropriate
place in your app to verify the Google Play services version. For example, if Google Play
services is required for your app at all times, you might want to do it when your app first
launches. On the other hand, if Google Play services is an optional part of your app, you can check
the version only once the user navigates to that portion of your app.

Another approach is to use the
isGooglePlayServicesAvailable() method. You might call this method in the
onResume() method of the main activity. If the result code is
SUCCESS,
then the Google Play services APK is up-to-date and you can continue to make a connection.
If, however, the result code is
SERVICE_MISSING,
SERVICE_VERSION_UPDATE_REQUIRED,
or
SERVICE_DISABLED, then the user needs to install an update. In this case, call the
getErrorDialog() method and pass it the result error code. The method returns a
Dialog you should show, which provides an appropriate message about the error
and provides an action that takes the user to Google Play Store to install the update.

To then begin a connection to Google Play services (required by most Google APIs such
as Google Drive, Google+, and Games), read Accessing Google APIs.